The octane requirement increase (ORI) effect exhibited by internal combustion engines, e.g. spark ignition engines, is well known in the art. This effect may be described as the tendency for an initially new or clean engine to require higher octane quality fuel as operating time accumulates, and is coincidental with the formation of deposits in the region of the combustion chamber of the engine. Thus, during the initial operation of a new or clean engine, a gradual increase in octane requirement (OR), i.e. fuel octane number required for knock-free operation, is observed with an increasing build-up of combustion chamber deposits until a rather stable OR level is reached. This, in turn, seems to correspond to a point in time where the quantity of deposit accumulation on the combustion chamber and valve surfaces no longer increase but remains relatively constant. This so-called "equilibrium value" is usually reached between about 4,800 and 32,000 km. or corresponding hours of operation. The actual equilibrium value of this increase can vary with engine design and even with individual engines of the same design. However, in almost all cases the increase appears to be significant, with ORI values ranging from about 2 to 14 Research Octane Numbers (RON) being commonly observed in modern engines.
Various types of additives are known which may prevent or reduce deposit formation, or remove or modify deposits, in the combustion chamber and adjacent surfaces and hence decrease OR. These additives are generally known as octane requirement reduction (ORR) agents.
Object of the present invention is to provide a gasoline composition containing an additive selected from a particular class of furan derivatives which exhibit a surprisingly high octane requirement reduction activity.